The present invention relates to fluid nozzles and, in particular, to hydraulic jet drilling wherein high-speed streams of fluid are emitted from nozzles mounted on the drill bit.
In a typical rotary drilling operation, a rotary drill bit is rotated while being advanced into a soil or rock formation. The soil or rock is cut by cutting elements on the drill bit, and these cuttings are flushed from the borehole by the circulation of drilling fluid toward the top of the hole. The drilling fluid is delivered to the drill bit downwardly through a passage in the drill stem and is ejected outwardly through nozzles disposed in the face of the drill bit. The ejected drilling fluid is directed outwardly through the nozzles at high speed (e.g., at 100 feet/sec. or greater) to aid in cutting of the rock and cooling of the drill bit.
In Radtke U.S. Pat. No. 4,381,825 issued May 3, 1983, nozzles are removably secured within a bore in the drill bit face. Preferably, the nozzles are attached in a readily replaceable manner, such as by means of a threaded connection between the nozzles and the bores in which they are positioned.
One problem which has arisen concerns the difficulty in replacing worn nozzles if the nozzles have been originally screwed-in with excessive force. Since the nozzles are normally manually screwed-in with a hand tool, it is difficult to control the amount by which the nozzle is tightened. Excessive tightening may cause the threads to bind and thereby cause extraction thereof to become excessively difficult.
It is, therefore, an object of the present invention to minimize or obviate problems of the type discussed above.
A further object is to prevent a nozzle from being excessively tightened.
An additional object is to provide a threaded member, such as a drill bit nozzle, which limits the amount by which it can be tightened.